This invention pertains to esters of lower aliphatic dibasic acids and fatty alcohol alkoxylates and more particularly to esters made from fatty alcohol alkoxylates or fatty alcohol adducts of alkylene oxides having 2 to 3 carbon atoms.
The increasing costs of energy have intensified the need for energy conservation in all phases of life. This is particularly true in the textile industry where large amounts of energy are needed in the heating of water used in the wet processing of fabric and yarn. The need for a cotton or polyester-cotton low-foaming surfactant having good low-temperature scouring properties is one of the needs which has arisen during the energy crisis.
One of the requirements for a low-foam surfactant is a significant measure of insolubility in the substrate liquid. With most nonionic surfactants, this is generally manifested in a low cloud point. Another requirement for a low-foam surfactant is that it must be a good surface tension depressant. The surfactant or surface active agent will concentrate at the surface of the liquid where foam will be degraded. At this point the surfactant must have the ability to lower the surface tension of the bubble wall to a point lower than that of the aqueous solution, resulting in rapid drainage of liquid from the bubble. The third requirement of low-foam surfactants, imposed by ecological restrictions, is ready biodegradability.
A class of nonionic surfactants used in the past have been prepared by alkoxylation of fatty alcohols to afford alkoxylates. It is also known that non-ionic surfactants can be prepared by the esterification of fatty alcohol alkoxylates. For example, Japanese patent application No. 46-17476 discloses the product obtained by reacting 10 moles of ethylene oxide with a C.sub.18 fatty alcohol followed by the reaction of the resultant ethoxylate with adipic acid. The use projected for this was as a lubricant for preventing polyester filaments agglutination. Its use as a low-foam scouring agent was not taught.
U.S. Pat. No. 3,382,285 discloses the composition obtained by the random addition of ethylene oxide and propylene oxide to a mixture of C.sub.12 to C.sub.20 fatty alcohols. These products are described as low-foam biodegradable surfactants.
U.S. Pat. No. 3,956,401 describes the preparation of low-foam biodegradable surfactants by reacting alkylene oxides with C.sub.7 to C.sub.10 alcohols.
Further, the reaction of dodecanol, succinic anhydride and polyethylene glycol (molecular weight 4,000) to yield nonionic surfactants was disclosed in Israel Pat. No. 38,521 (Chemical Abstracts, Volume 83, 117615, 1975). Here one carboxyl group was linked to the dodecanol and the other capped with an ethylene oxide adduct. No information is given as to the foaming properties of the resultant product.
There is also disclosed in U.S. Pat. No. 3,549,543 low foaming, washing, and cleansing compositions consisting essentially of a mixture of 3 types of polyoxyalkylene compounds, one of which compounds can be a fatty alcohol alkoxylate ester.
It is an object of this invention to provide low-temperature, low-foam scouring agents.
In accordance with the present invention there has been discovered a method of cleaning cotton or polyester-cotton articles under conditions of low temperature and low-foam which comprises contacting said cotton or polyester-cotton articles with a liquid cleansing agent comprising an aqueous solution of a nonionic scouring agent having the formula: ##STR1## wherein R is alkyl having from 11 to 18 carbon atoms or alkyl substituted phenyl wherein the alkyl contains about 7 to about 12 carbon atoms, A is a divalent radical selected from the group consisting of oxyethylene units and mixtures of oxyethylene units with oxypropylene units up to a ratio of about 1:1; z is an integer having values of 0 or 1 and y is an integer having values of 5 to about 12.
The mixed oxyalkylene units can be either a block or random ethoxy/propoxy combination obtained by using a mixture of ethylene oxide and propylene oxide in a condensation reaction with a fatty alcohol having 11 to 18 carbon atoms. A random combination of these oxyalkylene units is preferred. Blocks of ethoxy or propoxy units achieved by using alternate interaction of a fatty alcohol with the corresponding alkylene oxide afford scouring agents in the practice of this invention which have greater foaming tendencies, a property to be eschewed. The scouring agent of this invention is obtained by esterification of oxalic or malonic acid with fatty alcohol alkylene oxide adducts.
When, scouring agents containing mixed oxyalkylene units are used, it is preferred to use a large excess of oxyethylene to oxypropylene units. While up to 1 part of oxypropylene units per unit of oxyethylene can be used, one can also use an oxyethylene:oxypropylene ratio of about 50:1 or even a ratio of 100:1. Ratios below 1:1 cannot be used because the water solubility of the resultant scouring agent is too small for practical use.
Also provided in accordance with the present invention is a nonionic diester composition which is particularly suitable for use as a low-foam, low-temperature scouring agent when mixed with water having the formula: ##STR2## wherein R is alkyl having from 11 to 18 carbon atoms, A is a divalent radical selected from the group consisting of oxyethylene units and random mixtures of oxyethylene units with oxypropylene units up to a ratio of about 1:1; and y is an integer having values of 5 to about 11.
The compositions of the present invention are liquids having a low viscosity which have been found to exhibit a combination of low-foam, good scourability, good wetting, good biogradability, and excellent thermal stability characteristics. Further, they are suitable for use at low temperatures as evidenced by a cloud point of from about 10.degree. C. to about 40.degree. C., affording energy saving capabilities, and the thermal stability thereof makes possible their use in spray dried formulations.
The fatty alcohols used in making the alkylene oxide adducts from which the ester compositions prepared can be primary or secondary having 11 to about 18 carbon atoms. It is preferred to use alcohols containing 11 to about 14 carbon atoms. The alcohols may also be branched although it is preferred to use linear alkyl chains.
The degree of polymerization of the alkylene oxide adducts is about 5 to about 12. Preferably, when ethylene oxide is used in preparing the alkylene oxide adducts the degree of polymerization is from about 7 to about 9, and when random mixtures of alkylene oxides are used, the degree of polymerization is from about 7 to about 11.
The dibasic acid used for making the esters of this invention is, preferably, oxalic acid with malonic being a less desirable dibasic acid. Inferior results are obtained as one goes up in this homologous series as shown in the examples where adipic acid is completely unsatisfactory.
The diester, nonionic scouring agents suitable for use according to the process of the invention may be prepared by methods well known in the art. Various transesterification catalysts can be used, with titanium alkoxides being preferred and tetraisopropyl titanate being most preferred. The esterification reaction is enhanced by using a water-azeotroping agent such as benzene, toluene, and the like.
Esterification temperature is not narrowly critical, but it is preferred to use the temperatures in the range of 100.degree. C. to 180.degree. C., with a temperature range of about 140.degree. to about 170.degree. C. being preferred. Under these conditions, the reaction completed in about 8 to about 12 hours. Pressure is not critical.
The preferred scouring agent embodiments of this invention offer the following improvement over the prior art compositions:
1. improved wetting ability PA1 2. low-foam generation PA1 3. superior scouring ability at 100.degree. F. (37.5.degree. C.) PA1 4. readily bio-oxidized in 20 days PA1 5. liquid having a low viscosity PA1 6. excellent heat stability
The concentration of scouring agent is not narrowly critical but it is preferred to use aqueous solutions containing about 0.05 to about 0.2 weight percent of scouring agent therein.